Activation of sensory nerves in the upper airways by allergic inflammation, surgical intervention, airborne pollutants and tobacco smoke initiates cardiopulmonary and upper airway reflexes. Reflexes and sensations include sneezing, itch, congestion, mucus secretion, bronchospasm, altered respiratory pattern, arterial hypotension and bradycardia. The specific nature of a given reflex response is likely due to the type of upper airway afferent nerve that is activated. However, progress in this area has been limited by a lack of information regarding upper airways sensory nerve subtypes and their mechanisms of activation. In Aim 1, we will address the novel hypothesis that there are two distinct chemosensitive (nociceptor C-fiber) sensory nerve subtypes innervating the upper airways based on activation profile, neurotransmitter content and the area ofthe mucosa they innervate. In Aims 2 and 3 we will study the activation of these subt3rpes by key stimulants of upper airways-mediated reflexes. Specifically, in Aim 2, we will address hypotheses relating to the role of transient receptor potential Al (TRPAl) in the activation of upper airways nociceptors. TRPAl receptors are activated by a wide range of exogenous substances including pollutants, foodstuffs and tobacco smoke constituents. TRPAl receptors are also targets for downstream signaling events following G-protein coupled receptor activation (e.g. bradykinin B2 receptors). In addition we present the novel hypothesis that TRPAl receptors are directly activated by the endogenously-produced prostanoid 15-deoxy-deltal2,14-prostaglandin J2, a metabolite of PGD2. In Aim 3 we will address the hypotheses that specific mast cell mediators effect upper airway nociceptor activity via 2 distinct mechanisms: "activation" and "altered excitability". We will also evaluate the mechanisms by which these events occur. We will use a combination of anatomical and electrophysiological techniques to address our hjT)Otheses.